Bo Harald Giertz was born 31 August 1905 in Räpplinge, Borgholm, Öland (Kalmar), Sweden. He came from a prominent family and his father was a noted surgeon and head of one of Sweden's largest hospitals He was also an atheist. Bo planned to follow in his father's path and in 1924 he enrolled in the School of Medicine at the University of Uppsala. While there, however, theological students began challenging his belief system and, by the guidance of the Holy Spirit, he came to faith in Jesus Christ, left the school of medicine, and entered the University School of Theology.

In 1934, Giertz was ordained in the Linkoping Cathedral. He became assistant to the bishop and was given responsibility for working with the youth. His own faith and his conviction concerning the relevance of Christianity were on display for the thousands of young people who came under his care. Even as orthodox Lutherans lauded him, he also drew attacks from modernists in the Swedish state church and secularists as his writings spread in newspapers and periodicals. The public knew him as a talented and faithful confessor of a Church doctrine that was based in Scripture, confessed in the Creeds, and expounded in the Lutheran Confessions.

Giertz became a priest in Torpa in 1938, serving that parish until 1949, when he was consecrated as Bishop of Gothenburg. While serving Torpa, he wrote With My Own Eyes, a retelling of the Gospels (1947), four theological works, Christ's Church (1939), Church Piety (1939), The Great Lie and the Great Truth (1945), and The Battle for Man (1946), the catechetical book The Foundation (1942), and two novels The Hammer of God (1941) and Faith Alone (1943). These latter, particularly Hammer of God, became popular throughout Scandinavia and then around the globe.

The attention to theology and care for souls that Giertz evidenced in Torpa continued when he became Bishop of Gothenburg in 1949. As the youngest man elected and consecrated to serve the Church of Sweden as a diocesan bishop, he combined a somewhat pietistic type of pastoral care with High Church Lutheran theology, traits that are noticeable in his novels. Following the decisions of the Swedish Parliament and the Church Assembly to ordain women in the Church of Sweden (1958), Giertz became a leader of the opposition. In that same year, he invited all confessional groups in the Church of Sweden to form The Church Movement for Bible and Confession in response to the Assembly's decision.

The demands of the bishopric and the challenges of women's ordination and modernist theology slowed his writing for a time but once he became Bishop Emeritus, Giertz returned to the printed word in full force. He wrote The ABCs of Our Christian Faith in 1971, following it with The Knights of Rhodes (1972), another best-selling novel, the devotional books To Believe in Christ (1973) and To Live with Christ (1974), a new translation of the New Testament with Commentary (1977-1982), and, as a nonagenarian, he wrote The Living God — A Guide to the Christian Faith (1995). Most of Giertz's writings are not now available in English but new translations have begun to appear as the desire to read him grows.

Giertz pioneered a return to every Sunday celebration of the Lord's Supper, something that had largely vanished in the Church of Sweden due to the erosion caused by Pietism and Rationalism. He strongly urged pastors to pray the Daily Offices, something he applied in his own devotional life. Although often rejected by the leaders of the Church of Sweden, Giertz remains popular with true Lutherans in his own country, throughout Scandinavia, and across the world. Of him, the Reverend Hans O. Andrae wrote, "In his vision of the One Holy Christian and Apostolic Church, Giertz integrated a vibrant Evangelical-Lutheran orthodoxy, the Church's traditional liturgy, and sincere church piety into a harmonious and powerful wholeness."

O Lord God, heavenly Father, we pray that, as You raised up Bo Harald Giertz to lead Swedish Lutherans into a renewed appreciation of their confessional heritage and trust in the saving Gospel of Jesus Christ, and as You spoke to the entire Church through his writings, so You would continue to provide faithful pastors and leaders, keep us steadfast in Your grace and truth, defend us against all enemies of Your Word, and bestow on Christ's Church Militant Your saving peace; through Jesus Christ, Your Son, our Lord, who lives and reigns with You and the Holy Spirit, one God, now and forever.